April CET

[damianslaw]

Another small increase to 11.8C to the 9th. Perhaps another rise to 11.9C on tomorrow's update before things start to cool down.

A mean of 6.5C is now required just to reach the 1971-2000 average in the remaining 21 days, or 11.0C to beat the record set in 2007.

Cooling trend now on the cards, I very much doubt we will see come in higher than the 2007 value, but odds on above average I say - however, it could turn out only slightly above at this juncture. 3 mild CET months on the trot, how long will it last?

[reef]

Cooling trend now on the cards, I very much doubt we will see come in higher than the 2007 value, but odds on above average I say - however, it could turn out only slightly above at this juncture. 3 mild CET months on the trot, how long will it last?

Surpassing 2007 (itself an anomoly at 0.6C higher than the second warmest on record) would always be a tough job, but to get 2nd place a mean form the remaining 20 days of 10.0C would be required, something which is very possible if the last third is warm.

Hadley is now on 11.9C to the 10th. For some reason yesterday's value isnt showing in the list, but nevertheless it will probably be the peak point for the month. Its 5.3C above the rolling average, quite an exceptional warm spell!

[BornFromTheVoid]

11.9C to the 11th

http://www.metoffice.gov.uk/hadobs/hadcet/cet_info_mean.html

Yesterday was 11.5C. Minimum for today is rather high at 8.0C, while maxima look like being around 13C, so most likely a drop back to 11.7C or 11.8C tomorrow.

Looking ahead, the 06z GFS will have the CET at

11.4C to the 13th

11.0C to the 15th

11.0C to the 17th

10.7C to the 19th

[Thundery wintry showers]

Those figures illustrate how exceptional April 2007 was- an exceptiionally warm first 11 days, then something nearer average and already we end up half a degree short of April 2007!

[reef]

Those figures illustrate how exceptional April 2007 was- an exceptiionally warm first 11 days, then something nearer average and already we end up half a degree short of April 2007!

It was a bit of anomoly, not too dissimilar from May 1833 (though not as extreme).

I actually think we're still in with a shout of this being the second warmest April on record. We'd require a mean of 10.0C for the remaining 19 days. A more realistic target is probably hitting 10.0C - for that we'd require 8.9C.

Mean temperatures required in the remaining 19 days to give the following provisional CETs:

11.3C: 10.9

11.0C: 10.5

10.5C: 9.7

10.0C: 8.9

9.5C: 8.1

9.0C: 7.4

8.1C: 5.9

7.1C: 4.4

[Thundery wintry showers]

My original CET prediction of 10.2 is still looking quite good then!

[Kentish Kiwi]

I actually think we're still in with a shout of this being the second warmest April on record. We'd require a mean of 10.0C for the remaining 19 days. A more realistic target is probably hitting 10.0C - for that we'd require 8.9C.

Well GP seems to think its a definite possibility and that even 2007 could be in jeopardy: "Global model ensemble mean products are no in tune suggesting a ridge to develop close to our east and build back west as the trough in the Atlantic elongates and breaks up for the second half of the month. This is hugely significant as it places in the box seat to break records. Warmest April on record, driest March - April spell on record ?"

Would certainly be incredible to have the April record smashed so convincingly and then beaten just four years later... It is worth noting that April is a warming month and even if we have a cool middle period, it wouldn't be out of the question for temperatures to recover significantly in the last quarter of the month, especially considering what GP is suggesting.

[Milhouse]

Well GP seems to think its a definite possibility and that even 2007 could be in jeopardy: "Global model ensemble mean products are no in tune suggesting a ridge to develop close to our east and build back west as the trough in the Atlantic elongates and breaks up for the second half of the month. This is hugely significant as it places in the box seat to break records. Warmest April on record, driest March - April spell on record ?"

Would certainly be incredible to have the April record smashed so convincingly and then beaten just four years later... It is worth noting that April is a warming month and even if we have a cool middle period, it wouldn't be out of the question for temperatures to recover significantly in the last quarter of the month, especially considering what GP is suggesting.

Thats right. You have only got to look at recent warm Aprils and how they actually started off cool and rapidly warmed up later on to realize how much the second half of April is warmer than the first on average. If Aprils like 2003 and 2004 can end up well above average after such cool starts imagine how this one could turn out with it being almost 12c up to the 10th.

[Weather-history]

, driest March - April spell on record ?"

Definitely won't be the driest March-April spell on record.

Look at 1938, March 2011 was only 2.4mm drier than March-April 1938 combined

[North-Easterly Blast]

Yet again we avoid a cold April. It is now 22 long years since we last experienced an April more than 0.5*C below the long term CET average. Have cold Aprils gone from the UK climate forever?

For a low April CET, the most favourable synoptics are; frequent high pressure over Greenland pulling winds from the north / north-east across the UK, or frequent low pressure over or to the south of the UK bringing air of a polar maritime origin from the north-west.

Although Scandy Highs and easterlies are good for low CETs in the winter months, this sort of setup very infrequently is any good for a low April CET, as there is little cold air left on the continent by then. Air from the south to south east and Highs slap bang over the UK only equates to a high April CET, whereas a high slap bang over the UK in the winter months can give inversion cold at the surface and still deliver relatively cold conditions.

Although in 2009-10 and to a lesser extent in 2008-09 we have seen that we can still see good cold spells and cold persisting for most or a large part of the winter season, finally breaking a trend to mild winters overall that has persisted more or less throughout the 1990s and 2000s, and also in fact we did have a fairly cool May in 2010, a cold April still seems as far away as ever, and year after year it just never appears to be a trend that is broken.

Looking back at records, a cold month in one or more of the first three months of the year (Jan, Feb, Mar) has often worked well in leading to a cold April (1986, 1983, 1978, 1970, 1969, 1956, 1951, 1941, 1936, 1932, 1917, 1908 etc), with 1989 one of the few exceptions where a cold April has followed a very warm first quarter to the year. I thought in 2010 that there would have been a better chance of a cold April with Jan & Feb both below average and the cold persisting into March, but still a cold April plainly didn't happen.

In fact it is true that a cold winter overall has often been followed by good cold spells in the spring too and at least a March / April or both that are below average, or even sometimes May. Look at 1995-96, the cold persisted for most of March, and the mid 1980s winters, the cold persisted for most of March and in 1986 through April too. In 1978-79 the cold persisted through March and into April. This was also true in 1968-69 and 1969-70. Given what the winter was like in 2009-10, it was quite dissappointing that April and even March were not the sort of cold spring months that have followed many similarly cold winters.

Certainly 2010-11 has to be the record holder for the most extreme case of a pear shaped winter ever recorded in the UK, since the CET record began in 1659. For the combination of the most extreme pre Xmas freeze up on record deteriorating into nothing before December had even ended and how mild February was, and this spring so far especially this April, I cannot see any other winter / spring in the CET records that approaches it let alone beats it. Yes there have been other so called pear shaped winters in the past (winters that started off with a good cold spell early on but deteriorated into nothing) but none went belly up as early as 2010-11 did or saw an early freeze up of the level of pre Xmas 2010.

Winter 2010-11 is certainly an example to quote if severe cold sets in in late Nov / early Dec of how badly it faded by late December never to return, and despite how extreme the start of winter was, it was well spoiled with how the winter turned out post Xmas, and it was still a dissappointing winter for many.

Will we ever see a cold April EVER AGAIN? Every year that goes by and especially last year that failed to achieve a cold April after the sort of winter we had, just suggests to me that cold Aprils are now extinct, and that seeing another April like 1986, 1983, 1978 or something like the second half of April 1981 just seems out of the question now. The April we had in 2007 was just ridiculous, it brought all the spring flowers out far too early, bluebells, blossom treese, oil seed rape and all these were over by the time May began that year, and it just ruined what should be the time of year for all these to be out. Apr 2009 was also a very warm one too, persistently warm throughout. Now we are enduring another very warm April which will most likely end up in one of the ten warmest ever and could even break the 11.2 record of 2007. What we have seen over the last week has just been like the warmest and sunniest week in a typical May, and would be pleasantly warm even in June, it has just been ridiculous in April and even in the first ten days too.

Will this run of Aprils like this year and in many recent years ever end? Will cold Aprils ever return?

Of all the months in the year, April is the only one that has not seen a CET more than 0.5 below the current seasonal average in more than 20 years. No other month in the year has been devoid of a reasonably low CET for this long.

Comparing each set of averages, the 1961-90 April average is the lowest since 1911-40. 1971-2000 is 8.1, 1951-80 is 8.0, 1941-70 is 8.5, 1931-60 is 8.5. This is due to the fact that there were some very warm Aprils in the 1940s and mainly cold Aprils in the 1970s and 1980s.

[Weather-history]

. Have cold Aprils gone from the UK climate forever?

No

.

Will we ever see a cold April EVER AGAIN?

Yes

just suggests to me that cold Aprils are now extinct,

No

Will cold Aprils ever return?

Yes

Edited April 12, 2011 by Mr_Data

[TonyH]

[North-Easterly Blast]

No

Yes

No

Yes

Well the last 22 years have certainly shown that cold Aprils have become extinct. All the other months of the year have recorded one or more colder than average months since then, but April has been extinct from this. Last year given the winter that we got and how the cold persisted through the winter season and even into early March, after pattern matching from other years, I thought the chances must have been better for a cold April in 2010 than for many years, but it still plainly didn't happen. At a plus how the extreme pre Xmas cold in 2010 could fade so badly and lead to the rest of the winter being such a pile of pants since Xmas, and in particular the mild dross that February was, I was hoping for a cold April to make up for it or at least something of a surprise switch around to a late season cold spell, but we are still stuck in another one of the warmest Aprils on record.

Warm Aprils just seem to be a repetitive pattern every year and I am just so tired of it and am just desperate to see a change from this same pattern repeating itself year after year. There just seems to no way to say that it is still possible to get a cold April in the UK, when there hasn't been anything significant of a cold April in 22 years, this almost shows that cold Aprils are now impossible and are never likely to be seen again.

Edited April 12, 2011 by North-Easterly Blast

[Weather-history]

Well the last 22 years have certainly shown that cold Aprils have become extinct. All the other months of the year have recorded one or more colder than average months since then, but April has been extinct from this. .......

.... There just seems to no way to say that it is still possible to get a cold April in the UK, when there hasn't been anything significant of a cold April in 22 years, this almost shows that cold Aprils are now impossible and are never likely to be seen again.

No, what the last 22 years have shown is that there have been a lack of cold Aprils, it has not shown extinction. How can you deduce extinction from this? The answer is you can't because it only needs to return to one cold April in the next 1000 years to prove that a cold April is still possible and since we are still returning cold months including the 2nd coldest December ever recorded, it doesn't require one millimetre more extra logic to understand that a cold April is still very probable.

So what have we learnt?

Are cold months extinct? No

Deduction: April is a month therefore cold Aprils are not extinct.

I think if we divert the resources from the rant and into rational and logical thinking then it becomes clear.

Edited April 12, 2011 by Mr_Data

[Milhouse]

Didnt the majority of us say that sub zero winter months were a thing of the past and then we got last December. There have been many below average months in recent years, It just so happens that April hasnt been one of them.

[North-Easterly Blast]

No, what the last 22 years have shown is that there have been a lack of cold Aprils, it has not shown extinction. How can you deduce extinction from this? The answer is you can't because it only needs to return to one cold April in the next 1000 years to prove that a cold April is still possible and since we are still returning cold months including the 2nd coldest December ever recorded, it doesn't require one millimetre more extra logic to understand that a cold April is still very probable.

So what have we learnt?

Are cold months extinct? No

Deduction: April is a month therefore cold Aprils are not extinct.

I think if we divert the resources from the rant and into rational and logical thinking then it becomes clear.

We may have seen the second coldest December on record, but no-one can deny that it occurred as part of the most extreme case of a so called pear shaped winter ever recorded in the UK with no other winter in the CET record equalling how pear shaped 2010-11 was let alone beating it. Also December 2010 was also a sub zero month in the mildest winter on record that has contained a sub zero month, which puts an even greater emphasis on how pear shaped winter 2010-11 was and how much of a let down the rest of the winter was after the exceptional pre Xmas period.

There has certainly never been a winter prior to this year that has seen such a prolonged freeze up pre Xmas to dissappear completely before December is out never to return. Yes there have been a few very cold Decembers near or not far behind 2010; although the severe cold has rarely been maintained throughout the whole of the rest of winter, most of the winters with very cold Decembers have still seen further significant cold spells in Jan / Feb and even into the spring. Certainly for severe December cold to dissappear completely and abruptly as it did in 2010-11 has never happened before or at the very least not to that level.

I mean to say that seeing such extreme cold and widespread snow for so long in late Nov / early Dec just seemed so bizarre as it wasn't even Christmas for another three weeks, and then it is just so much of a let down for such a spell to deteriorate into nothing on Dec 27th - you haven't even got the Xmas / New Year festivities out of the way let alone anywhere near the end of winter, then a long two months or more to get through of nothingness looking for that ever elusive cold that never materialises before the time of year arrives for spring to begin. I certainly couldn't stand a repeat of 2010-11.

The same is true for what we have currently - seeing days on the trot of temps up to 20*C / 70*F in April is just utterly bizarre - its not even the beginning of summer for another seven / eight weeks, and it just brings all the spring flowers out far too early (bluebells, oil seed rape, tree blossom etc) and then it is all over by the start of May and ruins what May should be like, with all these flowers at their best - and then there is a gap before the proper time of year for summer. What we have now, what we had in April 2007 is just ridiculous - just when will, and will we ever see a cold April again?

Even before the half way point I think that anyone can be confident to call this April as one of the warmest on record for the UK - it will be very difficult now to avoid a 10*C+ CET finish, and the record warm April of 11.2 in 2007 is seriously under threat now, and could well be surpassed just four years later - and April 2009 was still very warm too and in the top 20.

To get a low April CET you need frequent high pressure over Greenland and winds from the N or NE, or low pressure crossing the south of the UK originated from a polar maritime source near Greenland - why can this setup not occur in April any more or at least for long enough - we came to it for about two weeks in April 2008, but the warm southerlies / or high pressure over the UK still occurred early on and in the final third of the month which wrecked the chance of a low CET.

[Thundery wintry showers]

We may have seen the second coldest December on record, but no-one can deny that it occurred as part of the most extreme case of a so called pear shaped winter ever recorded in the UK

Surely "so called" implies that a significant number of others use the phrase? I don't recall anyone else referring to 2010/11 as a "pear shaped winter"...

The switch-around from the record-breaking December to the remarkable snowlessness from mid-January onwards (and, for some, 27th December onwards) has been exceptional and probably unprecedented. But it's not as if unprecedented events don't happen- after all December came very close to breaking the CET record (and probably was the coldest December for 350+ years in parts of Ireland, Scotland and northern England) despite global temperatures being more than 0.5C higher than they were during the 17th, 18th and 19th centuries.

The absence of particularly cold Aprils has been noteworthy in recent years, and it may be compounded by the fact that recent 30-year means have been skewed downwards by the anomalously cold Aprils of the 1970s and 1980s. However, it is certainly possible to get a very cold April- just take the synoptics of the first half of April 2008 and keep them going for much of the second half, and there you are.

[North-Easterly Blast]

Surely "so called" implies that a significant number of others use the phrase? I don't recall anyone else referring to 2010/11 as a "pear shaped winter"...

The switch-around from the record-breaking December to the remarkable snowlessness from mid-January onwards (and, for some, 27th December onwards) has been exceptional and probably unprecedented. But it's not as if unprecedented events don't happen- after all December came very close to breaking the CET record (and probably was the coldest December for 350+ years in parts of Ireland, Scotland and northern England) despite global temperatures being more than 0.5C higher than they were during the 17th, 18th and 19th centuries.

The absence of particularly cold Aprils has been noteworthy in recent years, and it may be compounded by the fact that recent 30-year means have been skewed downwards by the anomalously cold Aprils of the 1970s and 1980s. However, it is certainly possible to get a very cold April- just take the synoptics of the first half of April 2008 and keep them going for much of the second half, and there you are.

What I mean is that a pear shaped winter is a winter that has a good cold spell to start with and then quickly deteriorates into nothing or even much milder than average - winters 1996-97, 1981-82, 1944-45, 1927-28, 1925-26, 1917-18 are all examples of what were pear shaped winters - but 2010-11 is the most extreme example of a pear shaped winter in 350+ years of records. No other winter has ever seen such an early freeze up deteriorating into nothing after Dec 27th - I mean to say the freeze up pre Xmas was totally unprecedented for so early in the season - and the winter post Dec 27th was very typical of the mild post 1988 era. Take out the period Dec 1st - 27th, and winter 2010-11 has a CET of 5.0*C, not the 3.1 that it ended up, to give a realistic idea of how pear shaped it was.

[Weather-history]

The same is true for what we have currently - seeing days on the trot of temps up to 20*C / 70*F in April is just utterly bizarre -

Its unusual but it has happened before such as 1893, I don't think its as amazing as breaking those December minima records on the trot.

I honestly don't know why you are worried or harping on about it. Go out and enjoy it, whilst it lasts!!!!!

Sitting about and moaning about it to this degree ain't gonna change it one bit. Its happened, its happening.

Edited April 13, 2011 by Mr_Data

[reef]

Hadley has fallen to 11.6C to the 12th on today's update. Today's update isnt showing on the page but 8.5-9.5C looks about right.

[Optimus Prime]

I'm now almost certain North-Easterly Blast is a newspaper journalist working for the daily mail.

[Milhouse]

Can someone tell me what the warmest April up until 2007 was. I have searched in the April 2007 thread but cant find any mention of it. I seem to remember 2007 beat the previous record by quite some way, which would make another record 4 years later even more remarkable.

[BornFromTheVoid]

Can someone tell me what the warmest April up until 2007 was. I have searched in the April 2007 thread but cant find any mention of it. I seem to remember 2007 beat the previous record by quite some way, which would make another record 4 years later even more remarkable.

10.6C in 1865 methinks.

[reef]

Hadley is now 11.2C to the 13th. Yesterday was slightly cooler than average at 7.2C.

Its difficult to judge where we're heading right now. Temperatures look pretty warm right out until the middle of next week on the GFS 6z, before a brief cooler blip. We then have a prolonged very warm spell in FI, which if it came to fruition, would probably see the 2007 record go.

Edit: A tally up of the temperatures shown on the 6z would give a final outcome of 11.3C.

[Roger J Smith]

About the warmest April so far, I mentioned earlier in the thread that in 1778, April stood at 10.9 after the 13th, and ended up at 8.2 C. There were no more days above 10.0 that month.